Solderless connecter lug



Patented June 15, 1937 SOLDERLESS CONNECTER LUG Ernest G. Johansson, Watertown, Mass assignor to The Palmer Electric & Manufacturing 00.,

' Waltham, Mass., a corporation of Massachusetts Application November 2, 1933, Serial No. 696,351 2 Claims. (01. 173-269) This invention relates to a method of and means for making an eflicient permanent. electrical connection between an electrical conductor, particularly one of substantial diameter, and

5 a binding post. i

In making electrical connections with conductors of considerable diameter such as solid or stranded copper wires commonly used for carrying currents of considerable amperage, it is 10 essential that good electrical connections of ample contact area be made at the terminals. Otherwise, there is danger of objectionable voltage drop at the connection, together with heat losses arising from excessive resistance at the point of 15 poor contact, such heat losses involving potential danger to the conductor itself and to any combustible material in the vicinity. In order to obtain an adequate and satisfactory electrical connection, it has been customary in the past to 20 employ connecter lugs having an open hollow at one end to receive the endo? the conductor to be connected, the opposite end portion of the lug being flat and transversely bored to receive a binding post. In using a lug of this type, it is 5 customary to strip a shortportion of an insulated conductor, then to solder the stripped end portion of the conductor securely into the open hollow. The lug, thus adequately connected to the conductor, was then ready to be mounted on 30 a binding post and to be clamped thereon as by a suitable nut. Inactual practice, there are many occasions when it is highly inconvenient, if not impossible, to solder a lug on the end of an electric conductor. For example, a lineman g5 working at the top of a pole may not have or be able touse facilities for soldering a lug onto the end of a conductor. Various attempts have been made to provide a lug which would furnish a Q satisfactory connection without the use of solder.

40 Such attempts have heretofore resulted in clumsy and expensive structures.

The present invention represents a successful solution of the problem of furnishing a practical and efficient lug which is adapted to be con- 45 nected to an electrical conductor efllciently and permanently without the use of solder. The invention may be embodied in a device which is a combination of a screw-thread cutter and clamp, the clamping being effected by a binding post 5 and nut thereon. The thread-cutting member is adapted toicut a screw thread on the end portion of the electrical conductor to be connected, this screw thread not only enlarging the interfacial area of contact between the conductor 55 and the connecting element, but also ensuring clean, bright surfaces for such contact. The thread-cutting elements are thereupon clamped tightly on the out threads by the clamping action of the nut on the binding post to which the connecting element is attached. This results in an adequate permanent electrical connection which can easily be made without special tools.

For a more complete understanding of the invention, reference may be had to the description of an embodiment thereof which follows, and to the drawing, of which Figure-1 is a. perspective view of a device embodying the invention.

Figure 2 is a section on the line 2-2 of Figure 1.

Figure 3 is a section on the line 3-3 of Figure 1. I

Figure 4 is a perspective view of a device similar to that shown in Figure 1 together with an end portion of an electric conductor in position to enter the device.

Figure 5 is a perspective view of the device and conductor after the end portion of the latter has entered the device.

Figure 6 is a section on the line 6-6 of Figure 5.

Figure 7 is a perspective view of the members shown in Figure 5 when mounted on and secured to a binding post.

Figure 8 is a perspective view of an end portion of an electric conductor, together with a device for increasing the size of such end portion.

Briefly, the invention consists in cutting a screw thread on the bared end portion of an electrical conductor, then clamping the threaded end portion between complementary threaded elements to ensure tight interracial contact between the threaded surfaces of the conductor and elements, and to prevent the conductor from working loose by reverse rotation. 40

Figures 1, 4 and 5 illustrate in perspective an embodiment of the invention consisting of a metal block In which may be conveniently of general rectangular shape. 'A screw threaded bore ll extends into this block from one end thereof, I

this bore being countersunk as at I! to provide a conical guiding surface to guide into the bore the end of an electrical conductor such as a stranded wire I 3, illustrated in Figure 4 The diameter of the bore H is such as to cause the threads therein to cut a screw thread on the electrical conductor l3, the latter being of metal which is considerably softer than that ofthe .blook ill. The block I0 is preferably made of brass or other rustless metal of sumcient hard- 5 ness to cut threads in the comparatively soft copper which is customarily used for electrical conductors. The block I0 is also provided with a longitudinal slot which extends into the block from the end opposite the countersink I2. As shown, the slot 20 extends for nearly the entire length of the block. For the purpose of the invention, it is necessary that the slot 20 intersect the bore II for a considerable portion of the length of the latter from its inner end. The slot 20 is also of lesser width than the diameter of the bore so that the intersection of a portion of the bore II by the slot 20 results in the formation of a pair of jaws 2| and 22 having .on their inner surfaces threaded portions 23 and 24, these threaded portions being wall portions of the bore II. In order to employ the block Hi to make an electrical connection, the block is screwed onto the end portion of a conductor l3. The guiding 20 countersink |2 tends to crowd the ends of the strands of the conductor l3 into the threaded bore so that, by rotation of the block I, a

screw thread is cut on the outer surface of the conductor l3 as the conductor advances longitudinally into the bore I I. This screw thread, by

reason of its valleys, offers an increased surface area on the conductor |3 for interfacial contact with the interior of the bore Since these faces are freshly formed as a screw thread is cut, a bright clean contact is thus obtained. As the end portion of the conductor comes opposite the slot 20, it turns easily in the bore since the threaded surfaces 23 and 24 can yield from each other slightly by reason of the slot and therefore do not bind the conductor. When the conductor |3 has penetrated a sufllcient distance into the bore II for adequate interfacial contact with the surfaces 23 and 24, the jaws 2| and 22 are pressed toward each other by suitable means with the result that the threaded surfaces 23 and 24 are pressed securely against the contacting portions of the conductor l3 so that the ridges of each thread are wedged into the valleys of its complementary thread and a tight connection is made. The conductor I3 is firmly gripped and reverse rotation thereof is prevented.

The invention is not limited to any particular means for pressing the jaws 2| and 22 toward each other for the purpose of clamping the conductor tightly within the bore II.

It is convenient, however, to employ for this purpose a binding post to'which the block "I is to be attached. To this end, the block may be provided with a transverse bore 30 extending therethrough from top to bottom and transversely intersecting the slot 20. The bore 30 is of sumcient size to receive easily a binding post 3|, which, as is customary, may be mounted on a suitable base 32. The binding post is provided with a nut 33 or its equivalent. By screwing the nut 33 tightly against the block l0 after the latter has been placed upon the binding post 3|, the jaws 2| and 22 are thus pressed toward each other. Thus, the operation of setting up on the nut 33 serves the double purpose of "clamping the end portion of the conductor l3 tightly between the Jaws 2| and 22, and of making a secure electrical connection between the'block l0 and the binding post 3|. It is obvious that, when the nut 33 is backed off to permit the disconnection of the block ill from the binding post 3|, the block III is thus released as to be readily removed from the end portion of the conductor l3 by reverse rotation. It is further evident that each time the block III is removed from or replaced on the end of the conductor I3, the contact faces of both the conductor and the block are cleaned and brightened.

Blocks l0 may be provided with bores of various sizes to receive the standard sizes of electrical conductors. In some cases, it may be desired to connect a conductor to a block having an over-size bore This may be done by increasing the size of the end portion of the conductor |3 by the addition of extra strands sufficient for the purpose. For example, the addition of two extra strands to a No. 6 stranded wire will increase its size to the equivalent of a No. 4 wire. To facilitate the addition of a pair of extra strands, I may provide a bent piece of singlestrand wire 40, as illustrated in FigureB. As shown, this auxiliary piece may consist of an intermediate portion 4| adapted to pass around somewhat more than half the circumference of the conductor 42. The member 40 has, in addition to the intermediate portion 4|, straight end portions 43 and 44, these portions being preferably of approximately the same length as the stripped end portion 42 of the conductor. Thus, when the intermediate portion 4| is seated against the end of the insulation 45 of the con- .ductor, the ends of the straight portions 43 and 44 are substantially flush with the end of the conductor 42. Thus the ends of all of the strands including 43 and 44 penetrate substantially equal distances into the bore II when the block I0 is screwed thereunto. By the use of such devices, a standard sized block I0 can be employed for conductors of various sizes.

It is evident that various modifications and changes may be made in the embodiments herein shown and described without departing from the spirit or scope of the invention as defined in the following claims.

I claim: 1

1. An electrical connection, comprising a block having a screw-threaded bore extending inwardly from an endthereof, said block being splitv from' the opposite end so that the bore is longitudinally intersected for a substantial portion of the length thereof from its inner end, an electrical conductor having a screw-threaded end engaged in said threaded bore, a binding post extending loosely through both split end portions of said block, and means on said binding post for pressing said split end portions of the block .toward each other whereby the end portion of the conductor is tightly clamped in said threaded bore.

- 2. An electrical connecter comprising a fixed binding post, a block of metal having a longi- 'tudinal threaded bore extending in from one jecting portion of said binding post and adjustable to press against said block.

ERNEST c4. JOHANSSON. 

